Electric plug construction



Jan. 16,. 19,34.

A. EQGRANT ELECTRIC PLUG CONSTRUbTION ISSheets-Sheet 1 Filed June 7, 1933 lNVENTO R ALBERTE. GRANT fi- ATTO NEYS Jan. 16, 1934. A. E. GRANT, 1,943,958

ELECTRIC PLUG coflsmucmou Filed June 'T-, 1955 '5 Sheets-Sheet 2 INVENTOR' ALBERTE GRANT ATTOQNEYS l Jan. 16, 1934. 1 A. E. GRANT ELECTRIC PLUG cous'muc'i'mu Filed June '7, 1933 3 Sheets-Sheet 3 INVENTOR ALBEH'ZZTfi '2'- W ATTOR EYS Patented Jab. 16,

UNITED STATES PATENT OFFICE.

isms: mcrmc'rwo cossrauc'rron Albert ll. Grant, New York, N. Is'as'sIgnor to Kerant Corporation, New York, poration of New York N. 1., a cor- Application Jnne'l, 103's. Serial No. 814384 a mm. (01. 200-51) 10 an attachment plug comprising an improved manual switch. I

Another object is to provide an attachment plug comprising a switch and a thermal responsive switch control mechanism with simple means 15 for critical adjustment thereof.

A further object is to provide a female attach- I ment plug having improved contact sockets, and other and further objects will appear from the following specification. '20 Referring to the drawings:

Figure 1 is a front elevation plug embodying my invention.

Figure 2 is a side elevation. Figure 3 is a view similar to Figure 1, showing 25 the plug with one half portion removed to reveal the internal parts, the removed section being shown therebelow in linked relation.

Figure 4 is a sectional view taken on lines 4-4 of Figure 1.

Figure 5' is a sectional view taken onlines 5-5 of Figure 1. Figure 6 is a fragmental section taken on lines 6-6 of Figure 3.

Figure 7 is a sectional view taken on lines 7-! u of Figure 1.

Figure 8 is a sectional view taken on lines 8-8 of Figure 3.

Figure 91s a view in perspective of the hinge link employed to secure the half portions of the. o casing in swinging relation adjacent the lower end, or face, of the plug.

Figure 10 is a view in perspective of one of the spring socket elements.

Figure 11 is a side elevation of one of the spring 45 socket elements.

Figure 12 is a vertical section taken on lines 12-12 of Figure 11.

Figure 13 is a perspective view of one of the conductor strips.

of an attachment gimme 14 is a view in perspective of the pivotswtich contact member, and Figure 15 is a sectional view taken on lines 15-15 of'l'igure 14. x The casing isformedintwolikehaifpor- .tionsofmouldedinsulatingmaterislsuchashard rubber. Each half portion is recessed, asshown mligure3,sothatwhentheysreheldtogether inassembledrelation,suitablepassagfl.eham. bers,partitionsandabutmentsareforrnsdinths walls of the casing properly receive andsupport the several parts housed therein.

At its top the casing comprises a tubular neck portion 21 thru which the current supply wires 22 extend for connection to the terminal binding screws 23-23. This neck portion is grooved externally on each opposite side at 24 to adapt it for firm gripping engagement by the helical wire guard 25 and a circumferential groove or recess 26 is provided at the base of'the neck portion to receive the lowermost convolution of the resilient wire guard, whereby the guard is firmly but removably secured around the neck. By this construction, the wire guard not only perform its usual function of protecting the insulation of the cabled wires 22 against fraying, but is also safely' relied upon-to hold the half portions of the casing in assembled relation at the upper end of the p us- Extending centrally inward from the face or base of the plug portions, a slot is formed at 27,

transversely bridging which pins 28--28 are formed integral with the portions of the casing whereby, the portions are secured in hinged relation by means'of a link 29. This link is stamped from resilient flat metal in the form illustrated in Figure 9 and has bifurcate ends adapted to snap over and grip the respective pins 28 with which it remains in swivelling engagement.

From the description thus far it will be apparent that to disassemble the half portions of the plug, as for connecting the current supply wires, it is only necessary to detach the wire guard 25 from the neck portion 21 and relatively swing the half portions apart, the portions remaining connected in hinged relation by the swivelling link 29, and that the casing may be readily reassembled by a reversal of these simple operations.

The binding screws 23 are respectively threaded thru drifted holes formed in the upper end of conductor strips 29' and 30 and are received, together with the margins of said holes, in recesses 31-31 formed in the interior walls of the casing. The strip 29' conforms to the inner wall of the casing and is riveted at its lower end to one of the spring socket terminals 32, as shown inFig'ure 4. Conductor strip '30 is secured to the casing at clamped to the anchor post as shown in Figure 3.

The pivoting switch actuator 36 extends thru a side wall of the casing; is made of insulatingv material and functions as a lever. It is formed in the shape a a knurled segment at the external .33 and is reduced in width and angularly bent at 'one of the spring socket members.

end to facilitate its manual operation, and its inner end wipingly engages the free end of a re silient strip conductor 39 which extends downwardly and is secured at its lower end to an angular conducting bracket 40 which, in turn, carries Adjacent its upper end the strip 39 is bent to provide an abutment for limiting the downward swing of the'inner end of the actuator 38 when operated to deflect the strip into the position screw 43, and a flat bifurcate plate 44 adapted to' straddle the inner end of the actuator 36. The upper inner edge surface of the actuator is cammed, as illustrated, and the material removed from the bifurcated end of the switch member is rolled back to provide a smooth bearing surface in contact therewith.

The screw 43 on which the switch member is pivoted extends thru a slot formed at 30 in the conductor strip 30 and is threaded or otherwise secured to an adjustment member 45. A torsion spring 46 is confined between the head of screw 43 and the bracket 42 of the switch member and serves to hold the switch member in firm electrical contact with the conductor strip 30. One end of this spring is anchored at the head of the screw and its opposite end is extended from the coil and bears against oneleg of the switch member plate 44, tending to swing the plate downwardly.

From the foregoing description, it will be seen that current will pass thru one side of the plug thru conductor 29 to a spring socket 32, and on the other side of the plug thru the conductor 30 to switch member 41 and thence thru the strip 39 to the other spring socket. Assuming the circuit to be closed, as illustrated in Figure 3, it will be apparent that if the outer end of the switch actuator'36 be moved upwardly; its inner end will swing downwardly against the strip 39 and deflect the strip from undertheend of the switch member which will thereupon be downwardly moved by the spring 46 into the position shown in broken lines of Figure 3, thereby breaking the circuit. Also, that if the outer end of the actuator be now moved downwardly, its cammed inner edge will elevate the switch member against the resistance of spring 46 and its inner end will swing above the end of the strip 39, whereupon the strip will instantly resume its normal vertical position and upon release of the actuator the switch member will again be supported on the upper end of the strip and held thereagainst by the "spring.

Although I have thus far described the switch mechanism for manual operation, the construction is particularly well suited where the plug is to be used in connection with electrical heating units and it is desired to break-the circuit at a predetermined optimum temperature. For this purpose I make the conductor strip 39 of bi-metallic material as ordinarily employed in thermal switches, 'so that heat conducted back thru the terminal sockets to the strip will deflect the strip from its supporting position under the switch To adjust the switch so that such automatic action may occur at any desired degree of temperature within a wide range, I have provided means for varying the position of the screw 43 on which the switch member is pivotally-carried in relation to the strip 39. As heretofore stated, the screw 43 extends thru a slot in the, conductor 30 and is secured in an adjustment member 45. This adjustment member is slidable underneath the conductor 30 and is angularly bent and tapped to receive a threaded screw 50 having a knurled head 51 of insulating material which extends externally of the casing. The'screw head is provided with a circular flange at 52 which sockets in recessed portions 53 of thecasing. Therefore, as the screw head is rotated, the members 45 and 41 are moved relative to the strip 39 so that the bifurcate end of the switch member will over extend the end of the bi-metal strip 39 a greater or lesser distance, as desired, and thereby require that the strip shall deflect a greater or lesser distance before withdrawing its support from the switch member.

' I have found the construction exceptionally well suited for thermal operation because of the fact that there is no tendency for the bi-metal' conducting strip to warp, there being no working strain placed upon it whatever beyond the small degree of effort necessary to overcome the slight friction of the switch member bearing on its upper free end.

It will be noted that although the two half portions of the casing are moulded in all respects alike, that openings are provided in one side of the casing wall thru which the head 51 of the- 58, respectively, indicate areas from which the wall has been broken away.

Each of the spring sockets comprises a pair of elements 60 (see Figure 10) which are in all respects alike and are formed of sheet brass or other suitable and resilient conducting metal.

Each element comprises a flat strip 61 formed with a lip at its lower end and connected thereadjacent at each edge by integral arms 62 to a strip portion 63 which is angularly bent above the strip 61 into alignment therewith and perforated to receive a rivet or screw. The two elements comprising one of the sockets are assembled together and to the lower end of conductor strip 29 by means of rivet 64 with the aligned portions 61 and 63 of the respective elements in flat facing abutment. The elements of the other spring socket are similarly assembled together andto the bracket 40 by means of a screw 65 which threads into the casing wall as illustrated in Figure 5.

As thus formed, the socket terminals comprise spring clips capable of receiving and firmly gripping terminal wires, pins or prongs or widely varying shapes and diameters 'over a considerable area, thereby insuring good mechanical connection and positive electrical contact.

.I claim;

1. An attachment plug comprising a casing formed in two portions linked together at one end, said portions complementing each other to form a neck-like inlet passage in communication nuance with the casing at its opposite end, and a helical spring wire cable guard adapted to removably surround and externally grip the. walls of said passage to hold the casing portions in assembled relation;

2. An attachment plug comprising a, casing formed in two portions complementary to each other and together forming a neck-like cable inlet passage at one end of the casing, a link pivoted to each portion of the casing at its opposite end connecting the portions in hinged relation, and a helical spring wire cable guard adapted to removably surround and externally clasp the walls of said passage to hold the casing portions in assembled relation.

3. A terminal clip formed of resilientconducting metal comprising a pair of Jaw plates normalto the other conductor and having its opposite ly in facing engagement, arms integral with the opposite side edges of each plate intermediate the length thereof and bent outwardly and upwardly therefrom, a strip portion integral with the arms of each plate, said portions being bent into facing abutment and joined together above the upper ends of the plates,- and said plates being flared other end of the casing, and a removable spring wire clasp adapted to externally grip the walls of said passage to hold the casing portions in assembled relation; wire binding terminals with in the casing adjacent the inner end of said passage; contact sockets carried in the casing each comprising a clip formed of resilient metal to provide a pair of. jaw plates faced together, arms integral with the side edges of each plate intermediate the length thereof and bent outwardly and upwardly therefrom, a strip portion integral with the arms of each plate, said portions being bent into facing abutment and joined together above the upper ends of the plates, and said plates being flared apart at their lower ends and adapted to receive and grip a terminal prong between them; and conducting means connecting said terminals with said sockets.

5. A switch comprising two conductors spaced apart, a switch member pivotally mounted in contact with one of said conductors and having a free end adapted to swing, a spring urging the free end of said member in one direction, a resilient strip of conducting metal secured by one end to the other conductor and having its opposite free end positioned to support the free end of said switch member in spring pressed contact thereon, and an actuator comprising a lever which, when moved in one direction is arranged to deflect said strip from its contacted supporting position and, when moved in the opposite direction, is adapted to release said strip and return said member against the resistance of said spring to its contacting position.

6. A thermal switch comprising two conductors spaced apart, a switch member pivotally mounted in contact with one of said conductors in movable relation thereto and having a free end adapted to swing, a spring urging the free end of said member in one direction, a resilient strip of conducting bimetal secured by one end free end positioned to support the free end of said switch member in spring pressed contact thereon, means whereby said member may be swung against the resistance of said spring, and means for adJustably positioning said member in relation to said strip.

7. An attachment plug comprising a casing formed in two portions complementing each other to form a cable inlet passage at one end thereof, wire binding terminals within the easing adjacent the inner end of said passage, contact elements carried by the casing adjacent the other end thereof, conducting means connecting one of said terminals to one of said elements, a conductor extending from the other terminal and a thermal switch interposed between said conductor and the other contact element, said switch comprising a member pivotally mounted in contact with said conductor in movable rela-.

tion thereto and having a free end adapted to swing, a spring urging the free end of said mem'- ber in one direction, a resilient strip of conducting bimetal connected by one end to said other element and having its' opposite free end .positioned to support the'free end-of said switch member in spring pressed contact thereon, means whereby said member may be swung againstthe resistance of said spring, and means for adconnecting one of said terminals to one of said justably positioning said member in relation to sockets, a conductor extending fromthe otherterminal and a thermal switch interposed between said conductor and the other socket, said switch comprising a member pivotally mounted in contact with said conductor in movable relation thereto and having a free end adapted to I swing, a spring urging the free end of said member in one direction, a resilient strip of conducting bimetal connected by one end to said other socket and having its opposite free end positioned to support the free end of said switch. member in spring pressed contact thereon, means whereby said member may be swung against the resistance of said spring, and means for adjustgtbrlly positioning said member in relation to said 9. The structure defined inclaim 8; said sockets each comprising a terminal clip formed of resilient conducting metal ,to provide a pair of jaw plates faced together, arms integral with the side edges of each plate intermediate the length thereof and bent, outwardly and upwardly therefrom a strip portion integral with the arms of each plate, said portions being bent into facing abutment and joined together above the upper ends of the plates, and said plates being flared apart at their lower ends and adapted to receive 1 and grip aterminal prong between them.

ALBERT E. GRANT. 

